1. Field of the Invention
The present invention relates to a thin film magnetic head including a inductive type writing thin film magnetic head and a method of manufacturing the same, and more particularly relates to a combination type thin film magnetic head constructed by stacking an inductive type writing thin film magnetic head and a magneto-resistive type reading thin film magnetic head on a surface of a substrate and a method of manufacturing such a combination type thin film magnetic head.
2. Description of the Related Art
Recently a surface recording density of a hard disc device has been improved, and it has been required to develop a thin film magnetic head having an improved performance accordingly. A combination type thin film magnetic head is constructed by stacking an inductive type thin film magnetic head intended for writing and a magnetoresistive type thin film magnetic head intended for reading on a substrate, and has been practically used. In general, as a reading magnetoresistive element, an element utilizing anisotropic magnetoresistive (AMR) effect has been used so far, but there has been further developed a GMR reproducing element utilizing a giant magnetoresistive (GMR) effect having a resistance change ratio higher than that of the normal anisotropic magnetoresistive effect by several times.
In the present specification, such AMR and GMR elements are termed as a magnetoresistive reproducing element or simply as MR reproducing element.
By using the AMR reproducing element, a very high surface recording density of several gigabits/inch2 has been realized, and a surface recording density can be further increased by using the GMR element. By increasing a surface recording density in this manner, it is possible to realize a hard disc device which has a very large storage capacity of more than ten gigabytes.
A height of a magnetoresistive reproducing element, i.e. MR Height(MRH) is one of factors which determine a performance of a reproducing head including a magnetoresistive reproducing element. The MR height MRH is a distance measured from an air bearing surface on which one edge of the magnetoresistive reproducing element is exposed to the other edge of the element remote from the air bearing surface. During a manufacturing process of the magnetic head, a desired MR height MRH can be obtained by controlling an amount of polishing the air bearing surface.
At the same time, the performance of the recording magnetic head is also required to be improved in accordance with the improvement of the performance of the reproducing magnetic head. In order to increase a surface recording density, it is necessary to make a track density on a magnetic record medium as high as possible. For this purpose, a width of a write gap at the air bearing surface has to be reduced to a value within a range from several micron meters to several sub-micron meters. In order to satisfy such a requirement, the semiconductor manufacturing process has been adopted for manufacturing the thin film magnetic head.
One of factors determining the performance of the inductive type writing thin film magnetic head is a throat height (TH). This throat height TH is a distance of a pole portion measured from the air bearing surface to an edge of an insulating layer which serves to separate a thin film coil from the air bearing surface. It has been required to shorten this distance as small as possible. The reduction of this throat height is also decided by an amount of polishing the air bearing surface.
Therefore, in order to improve the performance of the combination type thin film magnetic head having the inductive type recording head and magnetoresistive reading head stacked one on the other, it is very important to make the performance of the recording head and the performance of the reading head to be balanced with each other.
FIGS. 1-9 show successive steps of a method of manufacturing a conventional standard thin film magnetic head. In these drawings, A represents a cross sectional view cut along a plane perpendicular to the air bearing surface and B denotes a cross sectional view of a pole portion cut along a plane parallel to the air bearing surface. FIGS. 10-12 are cross sectional and plan views showing a finally manufactured completed thin film magnetic head. It should be noted that the thin film magnetic head is of a combination type in which the inductive type writing thin film magnetic head and reproducing MR element are stacked one on the other.
First of all, as shown in FIG. 1, an alumina (Al2O3) insulating layer 2 having a thickness of about 5-10 xcexcm is deposited on a substance 1 made of, for instance AlTiC.
Next, as shown in FIG. 2, a first magnetic layer 3 constituting a bottom shield which protects the MR reproduction element of the reproducing head from the influence of an external magnetic field, is formed with a thickness of 3 xcexcm.
Then, as shown in FIG. 3, after depositing an alumina insulating layer 4 of thickness 100-150 nm by sputtering, a magnetoresistive layer 5 made of a material having the magnetoresistive effect and constituting the MR reproduction element is formed with a thickness not larger than ten nano meters, and is then shaped into a given pattern by the highly precise mask alignment.
Then, as shown in the FIG. 4, an insulating layer 6 is formed again such that the magnetoresistive layer 5 is embedded within the insulating layers 4 and 6.
Next, as shown in the FIG. 5, a second magnetic layer 7 made of a permalloy is formed with a thickness of 3 xcexcm. This second magnetic layer 7 has not only the function of the upper shield layer which magnetically shields the MR reproduction element together with the above described first magnetic layer 3, but also has the function of one of poles of the writing thin film magnetic head.
Then, on the second magnetic layer 7, is formed a write gap layer 8 made of a non-magnetic material such as alumina and having a thickness of about 200 nm, and then after forming a magnetic layer made of a magnetic material having a high saturation magnetic flux density such as a permalloy (Ni:50 wt %, Fe:50 wt %) and an iron nitride (FeN), this magnetic layer is shaped into a desired pattern by means of the highly precise mask alignment to constitute a pole chip 9. A track width is determined by a width W of the pole chip 9. Therefore, in order to attain a higher surface recording density, this width W should be made as small as possible.
During the above process, it is preferable to form a dummy pattern 9xe2x80x2 which will connect the second magnetic layer 7 to a third magnetic layer. Then, a through hole may be easily formed after mechanical polishing or chemical-mechanical polishing (CMP).
In order to prevent an effective record track width from being widened, that is to say, in order to avoid a spread of a magnetic flux at one of the poles upon writing, a part of the write gap layer 8 surrounding the pole chip 9 as well as the second magnetic layer 7 constituting one of the poles are etched by means of an ion beam etching such as an ion milling. This condition is shown in FIG. 5, and this structure is called a trim structure. This part of the second magnetic layer 7 serves as the pole portion.
Next, as illustrated in FIG. 6, an insulating layer, e.g. alumina layer 10 is formed with a thickness of about 3 xcexcm, and then an assembly is flattened by CMP.
After that, after forming an electrically insulating photoresist layer 11 into a given pattern by means of the highly precise mask alignment, a first layer thin film coil 12 made of, for instance a copper is formed on the photoresist layer 11.
Continuously, as shown in FIG. 7, after forming an electrically insulating photoresist layer 13 on the thin film coil 12 by the highly precise mask alignment, the photoresist layer is sintered at a temperature of, for example 250-300xc2x0 C. to obtain a flat surface.
In addition, as shown in FIG. 8, a second layer thin film coil 14 is formed on the flattened surface of the photoresist layer 13. Next, after forming a photoresist layer 15 on the second layer thin film coil 14 with the highly precise mask alignment, the photoresist layer is flattened by baking it at a temperature of, for example 250xc2x0 C.
As described above, the reason why the photoresist layers 11, 13 and 15 are formed by the highly precise mask alignment process, is that the throat height TH and MR height MRH are defined with reference to a position of the edges of these photoresist layers on the pole portion side.
Next, as shown in FIG. 9, a third magnetic layer 16 made of, for example a permalloy and having a thickness of 3 xcexcm is selectively formed on the pole chip 9 and photoresist layers 11, 13 and 15 in accordance with a desired pattern.
This third magnetic layer 16 is brought into contact with the second magnetic layer 7 at a rear position remote from the pole portion via the dummy pattern 9xe2x80x2, and the thin film coil 12, 14 passes through a closed magnetic circuit composed of the second magnetic layer, pole chip and third magnetic layer.
Furthermore, an overcoat layer 17 made of alumina is deposited on the exposed surface of the third magnetic layer 16.
Finally, a side on which the magnetoresistive layer 5 and gap layer 8 are formed is polished to form an air bearing surface (ABS) 18.
During the formation of the air bearing surface 18, the magnetoresistive layer 5 is also polished to form a MR reproducing element 19. In this manner, the above mentioned throat height TH and the MR height MRH are determined. In an actual thin film magnetic head, contact pads for performing the electrical connection to the thin film coils 12, 14 and MR reproduction element 19 are formed, but they are not shown in the drawings. FIG. 11 is a cross sectional view cut along a plane parallel with the air bearing surface 18 showing the pole portion of the combination type thin film magnetic film manufactured by the processes explained above.
As shown in FIG. 10, an apex angle xcex8 between a line S connecting side edges of the photoresist layers 11, 13, 15 for isolating the thin film coil 12, 14 and the upper surface of the third magnetic layer 16 is an important factor for determining the performance of the thin film magnetic head together with the above described throat height TH and MR height MRH.
Furthermore, as shown in the plan view of FIG. 12, the width W of the pole chip 9 ad a pole portion 20 of the third magnetic layer 16 is small. Since the width of the track recorded on the magnetic record medium is defined by this width W, it is necessary to narrow this width as small as possible in order to achieve a high surface recording density. It should be noted that in this figure, the thin film coil 12, 14 is represented by concentric circles for the sake of simplicity.
Upon manufacturing the known combination type thin film magnetic head, there is a particular problem in the precise formation of the top pole on a protrusion of the thin film coil covered with the insulating photoresist layer along an inclined surface (Apex) thereof after forming the thin film coil.
In the known manufacturing method, upon forming the third magnetic layer, after forming a magnetic material layer such as a permalloy on the protrusion of the thin film coil having a height of 7-10 xcexcm by plating, a photoresist layer is formed thereon with a thickness of 3-4 xcexcm and then the photoresist layer is shaped into a desired pattern by means of the photolithography.
Here the photoresist layer formed on the protrusion of the thin film coil should have a thickness of at least 3 xcexcm, at a bottom portion of the inclined portion, a thickness of the photoresist layer becomes about 8-10 xcexcm.
The third magnetic layer formed on the protrusion of the thin film coil having a height of about 10 xcexcm as well as on the flat write gap layer has to be patterned such that the pole portion of the third magnetic layer near the edge of the photoresist insulating layers (for instance, 11, 13 in FIG. 7) has a width of about 1 xcexcm in order to realize a narrow track. Therefore, it is necessary to form a pattern having a width of 1 xcexcm in the photoresist layer having a thickness of 8-10 xcexcm.
However, such a fine patterning for forming the pattern having a width of about 1 xcexcm in the thick photoresist layer having a thickness of 8-10 xcexcm is very difficult. Upon exposure in the photolithography, the pattern might be deformed due to the reflection of light and the resolution might be decreased due to the large thickness of the photoresist layer. In this manner, it is particularly difficult to perform the precise patterning for the top pole which should be narrowed for realizing the narrow record track.
In order to mitigate the above mentioned problem, after forming the top pole chip which can be manufactured to have a narrow width and can realize the narrow record track, the third magnetic layer constituting the top pole is formed to be coupled with the top pole chip like as the above explained prior art. That is to say, the above mentioned problem is solved by dividing the magnetic head into the pole chip defining the track width and the third magnetic layer introducing the magnetic flux into the top pole.
However, the thin film magnetic head, particularly writing head has the following problems.
Since the end face of the third magnetic layer 16 is exposed to the air bearing surface 18, the magnetic flux might leak therefrom and an accurate writing operation could not be performed, and therefore the surface recording density could not be improved. In order to solve such a problem, it has been proposed that the end face of the third magnetic layer 16 is retarded inwardly from the air bearing surface 18. However, in this case, a contact area between the pole chip 9 and the third magnetic layer 16 is reduced. Therefore, a magnetic resistance might be increased, and an efficiency of the magnetic head might be decreased.
In order to increase the contact surface between the pole chip 9 and the third magnetic layer 16 for decreasing the magnetic resistance, one may consider that the pole chip is formed to have a large length in a direction perpendicular to the air bearing surface 18. However, in the known thin film magnetic head, since an edge of the pole chip 9 remote from the air bearing surface 18 defines a reference position at which the throat height TH is zero, if the pole chip is formed to have a large length, the throat height zero reference position becomes far from the air bearing surface and it is difficult to set the throat height precisely. In other words, in the conventional thin film magnetic head, the pole chip could not be extended inwardly beyond the throat height zero reference position.
In order to improve the inductive type thin film magnetic head as well as to reduce a size thereof, it is necessary to make the throat height TH as small as possible, and to this end, it is necessary to set the throat height accurately with reference to the throat height zero reference position. In the known combination type thin film magnetic head, the throat height zero reference position could not be sufficiently close to the air bearing surface, and therefore the particularly short throat height could not be realized in a precise manner.
It is an object of the present invention to provide a thin film magnetic head having a particularly short throat height, in which the above mentioned various problems of the conventional thin film magnetic head can be solved or mitigated, while undesired saturation and leakage of the magnetic flux can be avoided even if the pole portion is miniaturized.
It is another object of the invention to provide a method of manufacturing the thin film magnetic head having a particularly short throat height in an accurate and efficient manner with a higher yield, wherein the saturation and leakage of the magnetic flux can be avoided even if the pole portion is miniaturized.
According to the invention, a thin film magnetic head comprises:
a substrate;
a first magnetic layer supported by said substrate and having a recess formed in a surface thereof, said surface being opposite to a surface on which the first magnetic layer is supported;
an insulating layer formed in said recess formed in said surface opposite to the surface on which the first magnetic layer is supported by the substrate, said insulating layer being co-planar with said surface of the first magnetic layer;
a write gap layer formed along the co-planer surfaces of the first magnetic layer and insulating layer;
a second magnetic layer formed along a surface of said write gap layer remote from said substrate such that the second magnetic layer extends from a portion in which said insulating layer is not embedded to a portion in which said insulating layer is embedded;
a thin film coil formed along a surface of said write gap layer remote from the substrate such that the thin film coil is formed in an electrically isolated and separated manner;
a third magnetic layer coupled with a portion of a surface of said second magnetic layer remote from said write gap layer and magnetically coupled with said first magnetic layer at a rear portion remote from an air bearing surface; and
an air bearing surface formed on a basis of a throat height zero reference position which is constituted by an edge of said insulating layer embedded in the recess formed in the first magnetic layer.
In the thin film magnetic head according to the invention, said air bearing surface is formed such that the edge of the insulating layer embedded in the recess formed in the first magnetic layer is used as the throat height zero reference position. Since this throat height zero reference position is not deviated during the manufacturing process, it is possible to obtain precisely a desired throat height according to a designed value. Furthermore, a typical depth of the recess is about 0.5-2.0 xcexcm.
It is preferable that said second magnetic layer is made of a magnetic material having a higher saturation magnetic flux density than said third magnetic layer. When the second magnetic layer constituting the pole chip is made of the magnetic material having a higher saturation magnetic flux density, the saturation of a magnetic flux can be prevented and the writing operation can be performed efficiently. Moreover, since the front end of the third magnetic layer is retarded from the air bearing surface, undesired writing due to the leaked magnetic flux can be avoided. In this case, upon comparing with a case in which both the second and third magnetic layers are made of the magnetic material having a higher saturation magnetic flux density, there is an advantage that the treatment during the manufacturing process can be easy and a manufacturing cost can be reduced.
Furthermore, in the thin film magnetic head according to the invention, since the rear end of the second magnetic layer extends up to a position remote from the air bearing surface than the throat height zero reference position, although the front edge of the third magnetic layer is retarded from the air bearing surface, the second and third magnetic layers can be brought into contact with each other with a larger contact area, and thus the leakage of the magnetic flux can be mitigated.
Moreover, since the throat height zero reference position can be closer to the air bearing surface although the front edge of the third magnetic layer is retarded from the air bearing surface as explained above, the pole portion having a short throat height can be formed precisely. In other words, according to the invention, by extending the second magnetic layer beyond the throat height zero reference position inwardly, it is possible to attain accurately the thin film magnetic head having a very short throat height.
Further, in the thin film magnetic head according to the invention, it is preferable that the recess is formed in the first magnetic layer such that a side wall of the recess is tapered. This taper angle may be preferably 15-90 degrees. By proving the taper in the side wall of the recess, in a small thin film magnetic head having a has a throat height not larger than 0.5 xcexcm, the saturation of the magnetic flux is prevented, and thus the overwrite and NLTS characteristics can be improved.
According to the invention, a method of manufacturing a combination type thin film magnetic head, having at least an inductive type thin film magnetic head supported by a substrate comprises:
the step of forming a first magnetic layer on a surface of a substrate such that the first magnetic layer extends from an air bearing surface;
the step of forming a recess in a surface of said first magnetic layer such that the recess has an edge which is separated from the air bearing surface by a predetermined distance;
the step of forming an insulating layer in said recess such that a surface of the insulating layer is co-planar with a surface of a part of the first magnetic layer extending from the air bearing surface to said edge of the recess;
the step of forming a write gap layer on co-planar surfaces of said first magnetic layer and insulating layer;
the step of forming a second magnetic layer constituting a pole chip on said write gap layer such that the second magnetic layer extends from the air bearing surface to a position beyond said edge of the recess;
the step of a thin film coil on said write gap layer in an electrically insulated and isolated manner;
the step of forming a third magnetic layer such that the third magnetic layer is connected with a portion of said second magnetic layer retarded from the air bearing surface and is magnetically coupled with said first magnetic layer at a rear portion remote from the air bearing surface; and
the step of forming the air bearing surface by polishing.
In the manufacturing method according to the invention, the surface of the insulating layer formed in he recess of the first magnetic layer is formed to be co-planar with the surface of the first magnetic layer, and thus the write gap layer can be formed to be flat and the second magnetic layer formed on the write gap layer can be also flat. They can be formed easily to have desired dimensions and shapes, and the manufacturing yield can be improved.
Furthermore, in the method according to the invention, it is preferable that said second magnetic layer is made of a magnetic material having a higher saturation magnetic flux density than the third magnetic layer. Then, as compared with a case in which both the second and third magnetic layers are made of the magnetic material having a higher saturation magnetic flux density, there is an advantage that the treatment during the manufacturing process can be easy and a manufacturing cost can be reduced.
Moreover, since the throat height zero reference position can be closer to the air bearing surface although the front edge of the third magnetic layer is retarded from the air bearing surface, the pole portion having a short throat height can be manufactured accurately. That is to say, by extending the second magnetic layer beyond the throat height zero reference position inwardly, it is possible to manufacture precisely the thin film magnetic head having a very short throat height.